I have an antenna. I want to measure S-parameters of it using a network analyzer. The antenna has to be soldered to SMA cable for the measurement of S-parameters. After the calibration, will the measured S-parameter have contribution from the solder too?

If yes, what all parasitic will be there? How can I remove it?

  • \$\begingroup\$ Which antenne type do you have and which VNA? How do you calibrate it? Are you using port extension? \$\endgroup\$
    – stowoda
    Commented Jul 3, 2019 at 11:44
  • \$\begingroup\$ I am not using port extensions. It is E5071C VNA and the antenna is simply a wire connected to a board that works at 50 to 100 MHz frequencies. \$\endgroup\$ Commented Jul 3, 2019 at 11:46
  • \$\begingroup\$ When calibrating with the wire (you will later use for the antenna) attached, your reference plane will be just at the and of the cable's connector. Now If you attatch the antenna (soldered to another sma connector) you will measure not the antenna`s S11 but the connector to connector junction + the antenna. You will have an error. So why not just soldering the antenna directly (as short as possible) to the cable (removing the connector of course). I assume you are using semi ritchet cable? \$\endgroup\$
    – stowoda
    Commented Jul 3, 2019 at 12:28
  • \$\begingroup\$ By using just the semi ritchet cable soldered as shortly to the antenna as possible you will still end up with some nH in series and some hundreds of fF in parallel.. \$\endgroup\$
    – stowoda
    Commented Jul 3, 2019 at 12:30
  • \$\begingroup\$ @stowoda: That's semi-rigid \$\endgroup\$
    – JRE
    Commented Jul 3, 2019 at 13:19

1 Answer 1


The solder itself won't bother much.

The real problem lies in the fact you have to cut the cable and separate the conductors from the coax. This will drastically change the line impedance at that spot.

If you have a VNA, you would be able to "see" such soldered junctions. Not because of the solder, but because you had to separate the conductors and the insulators in the coax to be able to solder the connection.


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